Prostatitis and prostate cancer are extremely common diseases in men, but the relationship between these two diseases is unknown. While acute prostatitis is thought to be infectious in nature, the etiology of chronic prostatitis and chronic pelvic pain syndrome (CP/CPPS) and asymptomatic inflammatory prostatitis remains unclear. By studying Aire-deficient mice that have defective immune tolerance and develop spontaneous prostatitis, we have identified a novel prostate autoantigen. Moreover, we have found that CP/CPPS patients with biopsy-proven inflammation in their prostate glands possess immune responses to the analogous human protein, semenogelin (Sg). These results provide new evidence to support autoimmunity as a potential cause for chronic prostatitis. Moreover, by assessing for immune responses to Sg, we may be able to detect prostate inflammation in symptomatic or asymptomatic men. Animal models as well as clinical observations demonstrate that chronic inflammation can enhance the development or certain tumors. We hypothesize that chronic prostatitis contributes to prostate cancer development. The overall objectives of this proposal are to examine: 1) whether there is an association between an immune responses to the prostate autoantigen Sg and prostate cancer in humans; and 2) whether chronic inflammation can enhance the development of prostate cancer in mouse models. In specific aim 1, we will determine whether immune responses to Sg are associated with the presence of inflammation and/or prostate cancer in men undergoing prostate biopsy. In the specific aim 2, we will determine whether chronic prostatitis can alter the development of tumors in mouse models of prostate cancer. This proposal will provide insight in the role of chronic inflammation and prostate cancer development. Moreover, these results could provide a rationale for prostate cancer prevention by treating chronic prostatitis.